Modular Multilevel Converters (MMC) have emerged as the most promising and popular Voltage Source Converter (VSC) based topology. The advantages of the topology are well documented, and include reduced switching losses and lower harmonic distortion. Due to the large number of switching elements the MMC topology is difficult to simulate. Simulation tools are necessary to investigate the application of MMC configuration. There is now a need to simulate the MMC topology in real time in order to test physical MMC HVDC controls. In this paper, two MMC models developed by RTDS Technologies are introduced. A point-to-point HVDC test system is studied in order to demonstrate the accuracy of each model.